1. Field of the Invention
The invention relates generally to the operation of integrated circuits. More particularly, the invention relates to the conversion of a signal derived from a circuit operating from a low voltage power supply to a signal derived from a circuit operating from a high voltage power supply.
2. Background of the Invention
As the various components of a computer system, including the microprocessor, memory, and control logic have become smaller, the voltage level of the power supply utilized by these components has been reduced. This reduction has not occurred uniformly across all components, however, and as a result it has become necessary to interface components which operate at different voltage levels. A voltage supply conversion circuit that converts a signal of one voltage level to a signal of another voltage level is normally used to accomplish this interface.
Past implementations of conversion circuits have utilized an initial conversion circuit in combination with a driver circuit. The initial conversion circuit converts an input signal into a second signal of the desired high voltage level. The second high voltage signal is then applied to the driver circuit which drives the output to the appropriate logic level. This method can introduce too much delay when the transmission speed of the signal is critical, however, because the steps of converting and driving the signal are done sequentially.
Other previous implementations of conversion circuits have used a single driver circuit to improve transmission speed. These circuits, however, tend to leak current when in a static state because when the input signal to be converted is at a lower voltage than the output signal, the input signal is not sufficiently strong to completely close all DC current paths. This is unacceptable when a computer system design requires minimum DC current draw to minimize either current heating or power consumption, or both.